Safety and Tolerability of TOP-N53 Applied on Digital Ulcers in Patients With Systemic Sclerosis

The main goal of this clinical trial is to learn about how safe the new drug TOP-N53 solution is when it is applied to open wounds on the fingertip (digital ulcers) in people with an uncommon illness that results in hard, thickened areas of skin and additional problems with internal organs and blood vessels (systemic sclerosis). Another goal is to learn if different strengths of TOP-N53 can treat certain aspects of the illness. Men and women between 18 and 69 years of age with this illness may participate in the clinical trial. A parallel treatment with Sildenafil 20 mg is allowed for clinical trial participants. The main questions the clinical trial aims to answer are: * Does TOP-N53 cause medical problems at the fingertip wound after it is directly applied to the wound? * Does TOP-N53 affect certain aspects of the illness like blood flow in the fingertip wounds, itch, pain, redness, bruises and bleeding at or beyond the fingertip wounds? Researchers will compare TOP-N53 solution in different strengths to a placebo (a look-alike substance that contains no drug) to see if TOP-N53 works to affect the aspects of the illness listed above. Participants will receive one or two treatments with the placebo or different strengths of TOP-N53. The higher strength of the drug will only be given to participants after the lower strength was found to be safe. Participants will visit the clinic up to 8 times within a maximum of 31 days. 2 visits may be done by telephone. The doctors will ask questions to ensure that it is safe for the participants to be in the clinical trial, apply the drug and follow-up on any medical problem after the treatment. They will also test if the drug works to treat the illness by several test methods before and after the treatment. Participants will help to find out whether the drug works to treat the illness and is safe by answering questions in a diary at different timepoints before and after treatment.